海洋细菌Catenovulum sp. DP03两个右旋糖酐酶差异分析

Differential Analysis of Two Dextranases from Marine Bacterium Catenovulum sp. DP03

摘要:

右旋糖酐酶是一类能够专一性水解右旋糖酐α-（1，6） 糖苷键的糖苷水解酶，在食品工业以及龋齿的防治方面都有着重要的应用，其主要来源于微生物。提取海洋细菌Catenovulum sp. DP03的基因组并测序，从中挖掘编码右旋糖酐酶的基因，在大肠杆菌中进行异源表达，并对重组右旋糖酐酶性质进行比较分析。海洋细菌Catenovulum sp. DP03中含有两个编码右旋糖酐酶的基因GL002870与GL002872，其大小分别为2 511 bp和2 805 bp；编码的蛋白质Cadex2870与Cadex2872的3D结构与AoDex的结构相似，AoDex的催化区域Q418-D440分别对应Cadex2870的Q431-D453以及Cadex2872的Q425-D447。Cadex2870 与Cadex2872的比酶活分别16.2 U/mg和4 U/mg，最适催化温度分别为45 ℃与30 ℃，最适催化pH分别为7和8；Cadex2870水解右旋糖酐的产物为异麦芽七糖、异麦芽五糖、异麦芽四糖以及少量异麦芽糖；Cadex2872水解右旋糖酐的产物为异麦芽七糖、异麦芽五糖以及异麦芽四糖。证实海洋细菌Catenovulum sp. DP03中含有两个编码右旋糖酐酶的基因，这两个右旋糖酐酶的蛋白质结构以及酶学性质均有差异。

Abstract:

Dextranase can specifically hydrolyze the α-(1,6) glycosidic bond in dextran, and it has important applications in food industrial production and prevention of dental caries. It is mainly derived from microorganisms. The marine bacterium Catenovulum sp. DP03 was screened and the complete genome sequence was determined. The dextranase genes were cloned and heterologous expressed in Escherichia coli. Then the properties of recombinant dextranases were compared and analyzed. There were two dextranases genes found in DP03, i.e., GL002870 and GL002872 which were 2 511 bp and 2 805 bp, respectively. The 3D structure of Cadex2870 and Cadex2872 were similar to that of AoDex. The catalytic regions Q418-D440 of AoDex corresponded to Q431-D453 of Cadex2870 and Q425-D447 of Cadex2870, respectively. The enzyme activities of Cadex2870 and Cadex2872 were 16.2 U/mg and 4.0 U/mg, respectively. The optimum catalytic temperatures for Cadex2870 and Cadex2872 were 45 ℃ and 30 ℃ respectively and the optimum catalytic pH values were 7 and 8, respectively. The products of Cadex 2870 hydrolyzed dextran were maltoheptaose, maltopentaose, maltotetraose and a small amount of maltose. And the hydrolysates of Cadex2872 were maltoheptaose, maltopentose and maltotetraose. The marine bacterium Catenovulum sp. DP03 contained two genes encoding dextranase. The two dextranases were different in the protein structure and enzymatic properties.